Mr Bo has not been seen since March. Initially, party leaders were assumed to want to deal with his potentially divisive case before a once-in-a-decade leadership transition this Autumn.

In April, Mr Bo was removed from his post in Chongqing and placed under investigation for "serious breaches of party discipline". He could also eventually face criminal charges as an accessory to Mr Heywood's murder.

But no results have yet been announced, and it seems that China's leaders have had difficulty reaching a consensus on how to deal with him. It is possible, according to one diplomatic source, that a decision will be postponed until after the leadership change.

Meanwhile another trial has to take place – that of Chongqing's former Police Chief Wang Lijun, whose flight to the United States consulate in Chengdu exposed Mr Heywood's death and sparked the current crisis.

For the past few months, Mr Bo has been under the scrutiny of the party's own disciplinary commission, a body headed by a former

Chongqing party chief, He Guoqiang, who is thought to be an enemy of Mr Bo's.

However, the commission is dogged by internal party politics, and one of Mr Bo's allies, Zhou Yongkang, heads the security apparatus that would provide information and evidence on Mr Bo's alleged offences.

Judging by previous cases, it may take much longer to complete the process. It took three years before Chen Xitong, a former mayor of Beijing, was put on trial for corruption and 18 months to bring Chen Liangyu, the former party secretary of Shanghai, to court.